The present invention relates to new process for producing an acid fluoride compound having a vic-dichloro structure, which is useful for an intermediate compound for producing a starting monomer of a fluorinated resin.
A compound having a perfluoroalkyl chain having a vic-dichloro structure (a structure wherein one chlorine atom is bonded to each of two adjacent carbons) at its terminal and a fluorocarbonyl group (xe2x80x94COF) is useful as an intermediate compound for producing a material monomer of a fluorinated resin, or a fluororesin. For example, a compound having xe2x80x94CF2ClCFCl can be reacted with zinc and then dechlorinated to form an acid fluoride compound having a perfluorovinyl group (CF2xe2x95x90CFxe2x80x94). A perfluorovinyl group of such a compound is a polymerizable group and thus various fluorinated resins can be produced by polymerization of such a compound. The resulting fluorinated resins are useful resins excellent in heat resistance and chemical resistance.
Among the above-mentioned fluorinated resins, for example, a homopolymer of perfluoro(3-butenyl vinyl ether)[CF2xe2x95x90CFCF2CF2OCFxe2x95x90CF2] is used in various fields as a transparent fluorinated resin. A monomer of such a fluorinated resin, perfluoro(3-butenyl vinyl ether) is conventionally prepared by the following manufacturing route.
CF2xe2x95x90CFCl+IClxe2x86x92CF2ClCFClI(A)xe2x86x92CF2ClCFClCF2CF2I(B) CF2xe2x95x90CF2
(B)+fumic sulfuric acidxe2x86x92CF2ClCFClCF2COF(C) xe2x86x92CF2ClCFClCF2CF2OCF(CF3)COF(D) KF, HFPO
(D)+soda ash/glass beadxe2x86x92CF2ClCFClCF2CF2OCFxe2x95x90CF2(E) xe2x89xa7250xc2x0 C.
(E)+zincxe2x86x92CF2xe2x95x90CFCF2CF2OCFxe2x95x90CF2
Namely, CF2xe2x95x90CFCl is reacted with iodine chloride to form the compound (A),which is reacted with tetrafluoroethylene to form the compound (B), which is reacted with fuming sulfuric acid to form the compound (C). Further, the compound (C) is reacted with hexafluoropropylene oxide (HFPO) in the presence of an alkali fluoride such as KF etc. to form the compound (D), which is heated at least 250xc2x0 C. in the presence of soda ash or a glass bead to form the compound (E), which is reacted with zinc to prepare perfluoro(3-butenyl vinyl ether) through dechlorination.
Such a conventional process for producing perfluoro(3-butenyl vinyl ether) etc. has had a drawback such that an isomer, CF2ICFCl2, is produced as well as the compound (A) in a step of producing the compound (A). The amount of the isomer is difficult to control. Further, the conventional production process has been economically disadvantageous since it includes a lot of reaction steps and its starting material is expensive. In addition, there have been difficult problems such as corrosion of the apparatus and the handling of the reagents resulted from using iodine chloride and fuming sulfuric acid etc.
On the other hand, as a method of fluorinating all of Cxe2x80x94H bonds to Cxe2x80x94F in a hydrocarbon compound, there have been known a direct fluorinating methods using elemental fluorine (hereafter, a direct fluorination), and a fluorinating method using a product prepared by electrolyzing hydrogen fluoride in an electrolysis cell (so called as an electrochemical fluorination). As a direct fluorination, there have been known a fluorinating method in a gas phase (hereinafter, gas phase reaction) and a fluorinating method in a liquid phase (hereinafter, liquid phase reaction).
A process for producing an acid fluoride compound has also been known by way of a thermal decomposition of a perfluorinated ester compound having at least 16 carbon numbers. It has been described that such a acid fluoride compound can be prepared by using a hydrocarbon ester compound having a corresponding carbon skeleton as its starting material and by directly fluorinating it using elemental fluorine in a liquid phase (J. Am. Chem. Soc., 120.7117(1998)).
It has also been proposed that a process for reacting a perfluoroalkyl ester containing no chlorine atom in the presence of a nucleophile and a solvent to form a perfluoro acid fluoride (U.S. Pat. No. 5,466,877).
However, it has not been conventionally conceived nor proposed that an acid fluoride having a vic-dichloro structure such as perfluoro(3,4-dichlorobutyl vinyl ether, which is a precursor to perfluoro(3-butenyl vinyl ether), could be produced by the direct fluorinating method or the electrochemical fluorination reaction mentioned above.
The object of the present invention is to provide a process for producing an acid fluoride (III) having a vic-dichloro structure such as perfluoro(3,4-dichlorobutyl vinyl ether, which is a precursor to perfluoro(3-butenyl vinyl ether), in a short process from raw material available at a low cost. Conventionally, such a process was economically disadvantageous that it requires many reaction steps and high cost of the starting material and includes difficult problems such as corrosion of the apparatus and handling of the reagents resulted from using iodine chloride and fuming sulfuric acid etc.